Double carriage shear

ABSTRACT

A cutting machine for sheet materials having a pair of circular cutters mounted on parallel spaced axles, with the cutting edges of the cutters touching each other and being slightly overlapped. A steerable, power driven feeding arrangement permits the cutting of variable curves. Straight cuts of infinite length and circles are also possible.

United States Patent [191 Wutke DOUBLE CARRIAGE SHEAR Alwin O. Wutke,636 East 53rd Avenue, Vancouver, British Columbia, Canada [22] Filed:Mar. 29, 1971 [21] Appl. No.: 128,893

[76] Inventor:

[52] US. Cl. ..83/426, 83/435, 83/436 [51] Int. Cl. ..B23d 19/04 [58]Field of Search ..83/32, 46, 426, 425, 83/433, 435, 436

[56] References Cited UNITED STATES PATENTS 1/1967 .loa

Johnson ..83/426 X [4 1 Apr. 24,1973

Primary E.\'aminerGil Weidenfeld Att0rney-Fetherstonhaugh & Co.

[ 5 7 ABSTRACT A cutting machine for sheet materials having a pair ofcircular cutters mounted on parallel spaced axles, with the cuttingedges of the cutters touching each other and being slightly overlapped.A steerable, power driven feeding arrangement permits the cutting ofvariable curves. Straight cuts of infinite length and circles are alsopossible.

9 Claims, 6 Drawing Figures PATENTEUAPR 24 I975 sum 1 BF 3 w? an m V InINVEMTOR ALWIN 0. WUTKE ATTDRN IVS DOUBLE CARRIAGE SHEAR This inventionrelates to cutting machines and is particularly concerned with shearsfor cutting sheet materials including sheet metals.

At present, most cutting operations carried out on steel and other metalplates are done on shearing machines utilizing a pair of verticallyoriented cutting blades which shear the plate with a vertical cuttingaction. One disadvantage of this type of shearing machine is that thecut possible is length limited by the size of the cutting blades.Needless to say it is possible to build such a machine in various sizesbut the fact remains that for any particular machine there is alimitation on the size of cut that can be made. A second disadvantage ofthe standard type of vertical shear is that while it is possible to makecurved cuts including circular cuts by appropriately shaping the cuttingblades the machines are always limited to a cut defined by the shape ofthe blades installed. While any one machine can be adapted to makedifferent shaped curved cuts this can only be done by changing theblades. Thus, these machines have the drawback that the blade changingprocess is a time consuming one and the need for a number of sets ofblades is an added cost. It will also be recognized that even with anumber of interchangeable cutting blades the number of curved cuts thatcan be made are limited i.e. that in no sense is there an infiniteselection of curves that may be cut.

It is therefore a primary object of this invention to provide a cuttingmachine for cutting sheet materials including sheet metals without limiton the length of cut that can be made.

It is a further object of the invention to provide a cutting machineadapted to make curved cuts of infinite variety without modifying themachine in any way as, for example, by replacing cutting blades.

It is a further and related object of the invention to provide a cuttingmachine which includes power driven means for feeding the work piecesthrough the machine with the feeding means being steerable so that linesmarked on the work pieces can be followed by an operator.

According to the invention a cutting machine which meets the aboveobjects includes a pair of circular cutters carried on spaced parallelaxles with each of the cutters having a peripheral cutting edge, the twocutting edges being in touch with each other and slightly overlapped.Sheet material to be cut is fed between the circular cutters by afeeding arrangement which includes a friction wheel and a rotatableidler between which the sheet material to be cut is nipped. The feedingmeans preferably also includes an outfeed friction wheel and associatedidler which is positioned diammetrically opposite said infeed frictionwheel relative to said cutters. As an integral part of the feeding meansthere is included a steering mechanism by which the orientations ofthefeed wheels can be changed in a synchronized way so that they operatetogether to move the work piece relative to the cutters in a precise andpredetermined direction. This direction can be changed at will and in acontinuous fashion by the operator so that a cut of any curvedconfiguration can be made in the work piece.

The invention will be more fully understood from the followingdescription of a preferred embodiment thereof as read in conjunctionwith the accompanying FIG. 2 is a vertical cross-sectional view takenalong the line 2-2 of FIG. 1, 7

FIG. 3 is a schematic perspective view of the drive chain within themachine of FIGS. 1 and 2,

FIG. 3a is a schematic view showing cutters of the machine,

FIG. 4 is a cross-sectional view taken along the line 44 of FIG. 2, and

FIG. 5 is a horizontal section taken on line 5-5 of F IG. 2.

Referring to FIG. 1, a frame 10 is essentially made up of a lowercarriage track 12 consisting of a pair of I- beams 12 and a similarupper carriage track 14 also consisting of a pair of l-beams. The tracksare fixed at their ends to a pair of end plates 16 and 18. The bottomedges of the end plates act as footings whereby the machine is rested onthe floor, there being a third footing 20 supporting the lower tracks 12at their middles. End plates 16 and 18 also carry a pair of shrouds 22and 24 and co-operating doors (not shown) which serve as cabinetsenclosing certain parts of the drive chain for the machine, as will beexplaned in greater detail hereinafter.

Supported on the lower tracks 12 is a first carriage 26 while a similarcarriage 28 is supported on the top track girders 14. As can best beseen in FIG. 2, both carriages are supported on the tracks forhorizontal movement, the lower carriage being connected to the tracksthrough flanged bearing wheels 30, similar wheel 32 connecting the uppercarriage to tracks 14. As described below, the carriages each carry acircular cutter mounted on a horizontal axle, which cutters each carry aperipheral cutting edge with the two cutting edges touching each otherand being slightly overlapped (in the order of A; inch). It can be seentherefore that the sheet material being cut on the machine moves in ahorizontal plane between the two cutters i.e. between the upper andlower carriages. The reason that the carriages are mounted for lateralmovement is simply that the machine is therefore rendered capable ofaccommodating materials to be cut of different sizes. For example, if itwere desired to trim the edge off a wide piece of sheet steel, forinstance, the carriages would be moved well to the left of theirposition shown in FIG. 1. Furthermore, as is also explained in greaterdetail hereinafter, the machine of the invention is capable of cuttingfull circles and the fact that the carriages can be moved is utilized insetting up the machine to cut a circle of a particular desired diameter.In any case, it will be apparent that whether the carriages are beingmoved to accommodate a larger sheet of material or to cut a largercircle, it is essential that both carriages move as if they were onebecause it is essential under all circumstances that the pre-setcooperative relationship between the two cutters is maintained. Apreferred arrangement for achieving this single movement of thecarriages is illustrated in FIG. 1. At the right hand end of themachine, as seen in FIG.

l, a shaft 34 is mounted in a pair of vertically spaced bearings 36attached to end plate 18. Shaft 34 carries a pair of sprockets 38 onwhich are engaged a pair of drive chains 40. Each chain extends acrossthe width of the machine and is engaged on a sprocket 42 carried at oneend of an idler shaft 44. Each chain has its two ends fixed to eitherside of the carriage with which it is associated, with the other run ofthe chain passing through a hole in the carriage. Thus, as shaft 34 isrotated, the carriages are caused to move back and forth on tracks 12and 14, always doing so in a precise way so as to maintain the pre-setrelationship between the two cutters. To effect rotation of shaft 34there is fixed to its upper end a splined bevel gear 46 which may bemoved in and out of mesh with a bevel gear 48 carried by main driveshaft 50 by means of a suitable crank 52. Main drive shaft 50 is, inturn, driven by a chain 54 working on a sprocket 56 fixed to theopposite end of shaft 50, with the chain 54 having its lower end engagedon a sprocket 58 fixed to the output shaft of a gear box 60 connected,in turn, to a motor 62. The motor is reversible and suitable switchingarrangements are provided so that the motor can be rotated in eitherdirection whereby the carriages can be moved in either direction.

To summarize the foregoing, it can be simply stated that the twocarriages 26 and 28 each carry a circular cutter which are in contactwith one another and that there is provided an arrangement of chains,sprockets and gears whereby the two carriages may be moved together,utilizing power from the main driving motor, so as always to maintainthe same pre-set cooperative relationship between the two cutters.

The two cutters themselves can best be seen in FIGS. 2 to 4. They are alower cutter 66 attached to carriage 26' and an upper cutter 68 attachedto upper carriage 28. Each cutter is mounted for free rotation on itsown horizontal axle (shown schematically by lines 66A and 68A in FIG.3a) i.e. the cutters themselves are not positively driven but onlyrotate when a work piece passes between them. As a preferred expedient,each cutter is a disk of sufficient thickness (see particularly FIG. 3a)

- that two peripheral cutting edges designated A and B can be carried byeach cutter. Thus, when a first pair of cutting edges A becomes dull asecond fresh pair B can be putinto service simply by removing thecutters from their axles and turning them around. Preferably the cuttingedges A and B are built up with cutting tool steel on a tougher butmilder base plate but it will be appreciated that the nature of thecutting edges is dictated largely by the nature of the material which isto be cut on the machine.

As the sheets being cut move between the cutters it is necessary thatthe sheets be supported. This is obviously particularly true whencutting heavier materials and as machines manufactured in accordancewith the invention would be capable of cutting sheet steel up to of aninch in thickness, the supporting arrangement must be capable ofcarrying a considerable weight. In the preferred embodiment of theinvention which is illustrated in the drawings the sheet being cut issupported by a pair of rotatable tables 70 and 72, see particularly FIG.2. These tables are carried on central axles and havetheir outer edgessupported by three rollers 74 carried by brackets .76 which are mountedon transversely extending arms 77. As is explained hereinafter, tablesand 72 co-operate with an infeed wheel, 78 and an outfeed wheel 80respectively when work pieces are being fed through the machine. Theco-operation referred to simply means that tables 70 and 72 act asrotatable backstops against which the wheels 78 and 80 are pressed as tocreate a nipping action on the work piece moving through the machine.This being the case it will be appreciated that tables 70 and 72 arecanted slightly so that as the tables rotate they do not bind againstthe underside of the work piece. Additional support is provided byrollers 82 (FIG. 1) which are spaced some distance away from the centerof the machine. There are four of these additional support rollers, twoon either side of the center of the machine and attached to the topsurface of girders 12. As a preferred expedient support rollers 82 canbe moved from their illustrated positions should it be necessary to doso in order to properly support a work piece having an unusual shape.This adjustment of the rollers 82 is achieved by rotatably mounting saidrollers in transverse members 83 which are clamped to the tracks 12 bysuitable means, not shown, thus enabling them to be moved towards andaway from one another as required and to be secured at a selectedspacing.

Reference has already been made to an infeed wheel 78 and an outfeedwheel 80. These feed wheels are power driven and as previously mentionedthey move a work piece through the machine by pinching the work piecebetween themselves and the rotatable support tables 70 and 72. As apreferred expedient, feed wheels having different facings are providedand can be interchanged one for the other. Thus, plastic faced wheelsare used for cutting lighter gauge sheet iron and other lightermaterials while steel wheels provided with fine gripping teeth are usedfor handling thicker steel plates.

Both feed wheels can be independently raised and lowered. Thearrangement which permits this action can best be seen in FIGS. 2 and 5.Referring to infeed wheel 78 it can be seen that it is mounted on ahorizontal axle 83 (FIG. 5) which protrudes from a gear housing 84 whichis fixed to a lever 86 having its inner end pivotally connected to ahorizontal shaft 87 on a main body member 88 which depends downwardlyfrom upper carriage 28. A lever 140 is suitably connected intermediateits length to the housing 84 as shown at 141 in FIG. 5 and the inner endof this lever is universally connected at 142 to the body member 88.Thus, it can be appreciated that infeed wheel 78 is raised. and loweredrelative to support .table 70 by swinging lever 140 on its inner endpivot whereby the gear housing 84 is raised and lowered. To assist inthe raising and dropping of the infeed wheel a counterweighted lever(FIGS. 1 and 2) is fixed to the upper end of housing 84. The outfeedwheel 80 is raised and lowered in the same way by similar mechanism andit is also provided with its own counterweighted lever 92 (FIG. 2 only).In order to permit the operator to raise and lower the outfeed wheel 80while standing at the front of the machine i.e. to the left of themachine as viewed in FIG. 2 a suitable linkage arrangement is providedto extend through the upper end of the machine and which is operativelyconnected to the above described raising and lowering mechanism, thelinkage arrangement being generally indicated by the reference numeral94.

Both the infeed and the outfeed wheels can be swung about a verticalaxis. In the case of infeed wheel 78 this axis is aligned with thecenterline of gear housing 84 while in the case of the outfeed wheel 80the axis corresponds with the centerline of its equivalent gear housing85. Referring again to the infeed wheel, the housing 84 (see FIG. 4) ismade up of a fixed upper part and a rotatable lower part, rotatable,that is, about the axis just mentioned in the vertical centerline of thehousing. It can be seen, therefore, that as the lower part 'of housing84 is rotated relative to the upper part, in-

feed wheel 78 which stands to one side of the housing will swing aboutthe centerline of the housing. In this regard it will be noted thattables 70 and 72 are so dimensioned that when the feed wheels are swungto new positions they still can co-operate with the top surfaces of thetables to provide the nipping action necessary to move the work piecethrough the machine.

An important feature of the cutting machine of the invention is that itis possible to swing the feed wheels about the aforementioned verticalaxes while a work piece is moving through the machine. Indeed, thefeeding arrangement is such that the operator can continuously andaccurately steer the work piece as it moves through the cutters so thatcuts of variable curvature can be made. Needless to say, as the infeedwheel and the outfeed wheel are both working on the same work piece atthe same time they must be moved in unison i.e. moved in such a way thatthey are not working against each other with the infeed wheel trying tomove the work piece in a first direction and the outfeed wheel trying topull the work piece in another direction.

The steering mechanism which effects the required unified control of thefeed wheels includes a steering wheel 96 fixed to and adapted to rotatea horizontal shaft 98 which terminates within a housing 100. By suitablegearing means within housing 100 the rotation of shaft 98 is transferredto a vertical shaft 99 within the housing and depending therefrom. Thelower end of the latter shaft is connected to a lever arm 102 which, bymeans of a pair of links 104 and 106 effects rotation about a verticalaxis of a control member 108. In turn, rotation of the control membermoves a pair of connecting rods 110 and 112 having their outer endspivotally connected to lever arms 114 and 116 respectively which are inturn connected to the lower rotatable parts of housings 84 and 85respectively. Thus, it can be seen that the rotation of steering wheel96 will, through the various linkages mentioned, cause a rotation of thetwo housings and a reorientation of the feed wheels 78 and 80. In viewof the manner in which the connecting rods 110 and 112 are attached tothe control member 108, the two feed wheels are caused to move in unisoni.e. that when feed wheel 78 moves in one direction the outfeed wheel 80will move in a similar direction so that the two feed wheels alwaysremain parallel to one another.

As previously mentioned, cutters 66 and 68 are not driven in a positivesense but only rotate as a result of the movement of a work piecebetween them. The motive force for moving a work piece is derived onlyfrom the feed wheels, as previously mentioned. The power for driving thefeed wheels is, in turn, taken off main shaft 50 through bevelled gears121) and 122. The latter gear is fixed to the upper end of a centralvertical shaft with appropriate gearing contained within main housing 28to convert the rotation of that shaft to a horizontal output shaft 126.Engaged on the latter shaft by a sliding splined connection are a pairof sprockets 128 and 130. Engaged on the sprockets are a pair of chains132 and 134 which drive a pair of sprockets 136 and 138 connected tohorizontal shafts leading into the upper parts of housings 84 and 85.Contained within these housings are appropriate gearing arrangements forrotating the drive wheels, which gearing arrangements permit the lowerparts of the two housings to rotate relative to the upper parts aspreviously mentioned and which also eliminate any backlash when thedirection of rotation of the drive wheels is made (by changing thedirection of rotation of the drive motor 62 which in turn changes therotation of the drive shaft 50 etc.). These gearing arrangements areshown in detail in FIG. 4.

It should also be noted that there are occasions when it is advantageousto shift the infeed and outfeed wheels 78 and to the right or left asviewed in FIG. 1. To ensure that this is possible with wheel 78 forexample, lever 86 by which the housing 84 is attached to the main body88, has its inner end slidably i.e. its pivoted end mounted on the shorthorizontal shaft 87 which is fixed to the main body member 88. Thus, thewheel 78 can be moved as described by means of the lever 140 while thesimilarly mounted wheel 80 can also be adjusted vertically andhorizontally by its lever 140 operated through the linkage arrangement94.

For cutting circles a movable center punch 144 is located at a pointequidistant between the two support rollers 82 on the right hand side ofthe machine as viewed in FIG. 1. This center punch has a pointed lowerend of sufficient hardness that it can be forcibly recessed (by suitablemeans, not shown) into the top surface of a work piece with the lowersurface of the work piece immediately beneath the pointer being nestedby a support block (not shown). The right hand (FIG. 1) support rollers82, the center punch 144 and the underlying support block all areappropriately mounted on the frame 10 so as to be shiftable to one sideor the other so that the diameter of the circular cut to be made isselected by locating the assembled unit consisting of center punch 144and its support block at the appropriate distance from the cutters.

Referring now to FIG. 4, the gearing arrangement for driving infeedwheel 78 is contained within housing 84, as previously mentioned. It isthe purpose of this arrangement to convert the rotation of sprocket 136to a rotation of wheel 78 while, at the same time, permitting relativemovement between the upper and lower halves of the housing andpreventing any backlash effects as the direction of rotation of the feedwheel is reversed. The gear train connecting sprocket 136 to wheel 78 isas follows.

The sprocket is connected to the splined outer end of a first shaft 137supported within thrust bearings and carrying a bevel gear 139 at itsinner end. The latter gear is in mesh with a pair of similar gearsconnected respectively to a second shaft 141 and to rotatable sleeve143. Thus, rotation of shaft 137 effects opposite rotations of shaft 141and sleeve 143. The latter carry another pair of bevel gears at theirother ends which are in mesh with gear 145 fixed to output shaft 147carrying infeed wheel 78 at its outer end. Thus, the above describedchain and sprocket arrangement provide a torque compensator so that,when the direction of rotation of shaft 137 is changed, there is nodelay in response by shaft 147 such as would occur if only a single gearchain were used.

While the manner in which the cutting machine of the invention isoperated should be understood from the foregoing description of themachine the following summary of the operating procedure will serve toemphasize the versatility of the machine. First of all it should beunderstood that the machine operator stands in front of the machine i.e.on the left side of the machine when the latter is viewed as shown inFIG. 2. The operator is equipped with a switching cable by which he caneasily stop and start the motor 62 as well as change its direction ofoperation. Thus, if at any time the operator wants to move a work piecebackwards i.e. to the left in FIG. 2 he can readily do so simply byreversing the motor. In the normal course, however, the infeed wheelrotates in the direction necessary to move the work piece to the rightwith the outfeed wheel 80 doing the same. The setup shown in thedrawings is the arrangement to effect straight cuts and it will beappreciated that by the use of circular cutters it is possible to makeinfinitely long cuts.

As a first step, the operator will manually feed the end of the workpiece along the top surface of table 70 until its leading edge contactsthe cutters 78 and 80. While this is being done infeed wheel 78 willhave been raised upwardly by means of lever 140 so that the operator hasno difficulty in manually manipulating the leading edge of the workpiece. Once the leading edge contacts the cutters, however, the operatorwould not normally be able to forcethe work piece between the cutters sothat the infeed wheel 78 must be brought into operation. This -is doneby lowering the feed wheel by means of lever 140 until the work piece istightly nipped between the infeed wheel and the top surface of table 70.At this stage counterweighted lever 90 prevents the infeed wheel fromrising i.e. the wheel is pressed tightly against the top surface of thework piece and is locked in that position.

The motor is then started so that the main shaft is rotated and by thevarious gearing arrangements previously described the rotation of thedrive shaft 50 is eventually transmitted to infeed wheel 78. Thus, thework piece is forcibly driven between the cutters and eventually. itsleading edge reaches the area of the outfeed wheel 80. At this stage theoutfeed wheel 80 is lowered down onto the top'surface of the work pieceby the mechanism 94. Thus, both the infeed and the outfeed wheels arebrought into play and as they always work in a co-operative fashion,very accurate control on the movement of the work piece can be achieved.When cutting a curve the operator simply manipulates steering wheel 96,utilizinga pointer (not shown) at the front end of the machine forfollowing a curve marked on the work piece. In other words, he utilizessteering wheel 96 to see that the curve marked on the work piece istranscribed by the pointer i.e. the direction of movement of the workpiece is changed so that the pointer can follow the curve marked on thework piece by swinging the infeed and outfeed wheels about theaforementioned axes through the centers of housings 84 and 85.

As previously described, larger or smaller work pieces can beaccommodated by shifting the carriages to the right or left, utilizingthe power take-off arrangement at the right hand end of the machine fortaking power from main shaft 50 to shift both the upper and lowercarriages carrying the upper and lower cutters respectively the sameamount. Also, of course, circular cuts can be made by utilizing thecenter punch 144 with the diameter of the circular cut to be made beingdetermined by the location of the center punch and/or the position ofthe upper and lower carriages.

I claim:

1. A cutting machine for cutting sheet materials, said machinecomprising a frame, a pair of circular cutters carried on spaced,parallel and horizontal axles attached to the frame one above the other,said cutters each having a peripheral cutting edge, said cutting edgestouching and being overlapped with each other, feed means for feedingwork pieces of sheet material between said cutters, said feed meansincluding a pair of power driven feed wheels carried on horizontalaxles, one on either side of said cutters whereby one feed wheeloperates as an infeed wheel while the other operates as an outfeedwheel, rotatable work piece support devices arranged beneath each ofsaid feed wheels, said feed wheels being operative to move a work pieceby a nipping action in which the work piece is squeezed between thewheels and the rotatable support devices, and a feed means steeringassembly for changing the orientation of said feed wheels whereby thedirection of feed of a work piece can be varied as to effect curved cutsin the work piece.

2. A cutting machine as claimed in claim 1, in which said steeringassembly includes a parallel linkage system for keeping said feed wheelsin parallelism as the orientation of said feed wheels is changed.

3. A cutting machine as claimed in claim 2, in which each of saidcutters is carried'on a separate carriage, said carriages being mountedon tracks forming part of said frame, for horizontal movement, andcoupling means interconnecting said carriages whereby said carriages aremoved together thereby maintaining the presetcooperative relationshipbetween said cutters.

4. A cutting machine as claimed in claim 3, in which said feed wheelsare carried by the uppermost carriage and including means forindependently raising and lowering said feed wheels relative to saiduppermost carriage whereby said feed wheels can be independently lowereddown onto a work piece. 7

5. A cutting machine as claimed in claim 4, in which said infeed wheelis mounted on said uppermost carriage for horizontal movementrelative'thereto whereby said infeed wheel can be offset relative tosaid cutters.

6. A cutting machine as claimed in claim 5, in which said rotatablesupport devices are circular tables positioned beneath said feed wheelson central vertical axles, the tables being canted slightly relative tothe horizontal so that as a work piece passes over said tables under theinfluence of the feed wheels pressing thereagainst, the work piece doesnot bind against the top surface of the tables.

second pair of cutting edges can be brought into opera 1 tion when afirst pair becomes dull.

9. A cutting machine as claimed in claim 8, including a center punchcarried by the frame of the machine to one side of said cutters wherebya circular cut may be made in a work piece by pressing the center punchagainst the work piece so that the work piece rotates about the centerpunch as it is moved through said cutters by said feed means.

1. A cutting machine for cutting sheet materials, said machinecomprising a frame, a pair of circular cutters carried on spaced,parallel and horizontal axles attached to the frame one above the other,said cutters each having a peripheral cutting edge, said cutting edgestouching and being overlapped with each other, feed means for feedingwork pieces of sheet material between said cutters, said feed meansincluding a pair of power driven feed wheels carried on horizontalaxles, one on either side of said cutters whereby one feed wheeloperates as an infeed wheel while the other operates as an outfeedwheel, rotatable work piece support devices arranged beneath each ofsaid feed wheels, said feed wheels being operative to move a work pieceby a nipping action in which the work piece is squeezed between thewheels and the rotatable support devices, and a feed means steeringassembly for changing the orientation of said feed wheels whereby thedirection of feed of a work piece can be varied as to effect curved cutsin the work piece.
 2. A cutting machine as claimed in claim 1, in whichsaid steering assembly includes a parallel linkage system for keepingsaid feed wheels in parallelism as the orientation of said feed wheelsis changed.
 3. A cutting machine as claimed in claim 2, in which each ofsaid cutters is carried on a separate carriage, said carriages beingmounted on tracks forming part of said frame, for horizontal movement,and coupling means interconnecting said carriages whereby said carriagesare moved together thereby maintaining the pre-set cooperativerelationship between said cutters.
 4. A cutting machine as claimed inclaim 3, in which said feed wheels are carried by the uppermost carriageand including means for independently raising and lowering said feedwheels relative to said uppermost carriage whereby said feed wheels canbe independently lowered down onto a work piece.
 5. A cutting machine asclaimed in claim 4, in which said infeed wheel is mounted on saiduppermost carriage for horizontal movement relative thereto whereby saidinfeed wheel can be offset relative to said cutters.
 6. A cuttingmachine as claimed in claim 5, in which said rotatable support devicesare circular tables positioned beneath said feed wheels on centralvertical axles, the tables being canted slightly relative to thehorizontal so that as a work piece passes over said tables under theinfluence of the feed wheels pressing thereagainst, the work piece doesnot bind against the top surface of the tables.
 7. A cutting machine asclaimed in claim 5, in which the drive chain for powering said feedwheels includes torque compensators to prevent back lash effects as theoriEntations and direction of rotation of said feed wheels are changed.8. A cutting machine as claimed in claim 7, in which said cutters eachhave two cutting edges, said cutters being reversibly mounted on theiraxles whereby a second pair of cutting edges can be brought intooperation when a first pair becomes dull.
 9. A cutting machine asclaimed in claim 8, including a center punch carried by the frame of themachine to one side of said cutters whereby a circular cut may be madein a work piece by pressing the center punch against the work piece sothat the work piece rotates about the center punch as it is movedthrough said cutters by said feed means.